So you basically want to do something like this -->
https://badbitcoin.org/ for ICO's? These guys have been around since 2014 and they did a fine job.
I think the most important aspect of a site like this is the trust factor. People must trust that the information provided on your site is valid and not some scam to eliminate the competition. 
This is exactly the sort of site that works, over the long run. Expose some of the general myths that scams purport like "mining BTC" or "cloud mining" or "generate BTC". Write about the modus operandi, like those watch wallet scams people keep falling for.
But yeah. They have shitty SEO so won't appear on Google searches I'm trying, I don't see how newbies might land on their site unless they search a specific ICO or website keyword that they have a review done on.
You've got a good point about the gambling sites as an example of how the trust works in unintended ways. Some casinos take care of the big guys and the reviewers, and surreptitiously dump out the small fish who doesn't have enough credibility to get noticed or taken seriously if they were to complain. I can easily see how the same trust system for review sites would be abused in the same way.
Ultimately, OP, you can't make a site that reviews or rates individual services. Those regulatory blacklists (like the Swiss and French market/investment regulators) put out blacklists every few weeks but that's far, far from comprehensive. For every review you can do, probably ten new sites pop up. You've got to focus on education and awareness instead.
when it looks too good to be true...
